Solid capacitor and manufacturing method thereof

ABSTRACT

A solid capacitor and the manufacturing method thereof are disclosed. The solid capacitor consists of a dielectric layer and two electrodes. A plurality of holes formed by an opening process is disposed on surface of the dielectric layer. The two electrodes connect with the dielectric layer by the holes. By means of a plurality of high temperature volatile matters, the plurality of holes is formed on surface of the dielectric layer during sintered process. The holes are connected with the outside so as to increase surface area of the dielectric layer and further the capacity is increased. And the solid capacitor stores charge by physical means. Moreover, the solid capacitor can be stacked repeatedly to become a multilayer capacitor.

RELATED APPLICATIONS

This application is a Divisional patent application of application Ser.No. 11/274,129, filed on 16 Nov. 2005, now U.S. Pat. No. 7,495,891.

BACKGROUND OF THE INVENTION

The present invention relates to a capacitor, especially to a solidcapacitor that increases the capacity by means of larger surface area ofthe dielectric layer thereof. Moreover, the solid capacitor inaccordance with the present invention can be stacked repeatedly so as toform a multilayer capacitor.

A capacitor is an energy storage component applied in circuits fortuning, filtering, coupling, by-pass, energy conversion and delay. Mostcommon used capacitors are electrolytic capacitors, mica capacitors,ceramic capacitors and vitreous-enamel capacitor. The names refer to thetype of dielectric that is used within the capacitor.

capacitor types structure and features aluminum An aluminum cylinderworks as a electrolytic cathode with liquid electrolyte thereincapacitor and a curved aluminum piece is used as an anode. The flow ofdirect current causes an insulating metal oxide to grow out of and intothe surface of the anode. The metal oxide is used as dielectric. Theadvantage of electrolytic capacitors is the high capacity per unitvolume. The disadvantage of electrolytic capacitors is the non-ideal,lossy characteristics and poor stability. It is used for signalcoupling. In usage, please note that the voltage should not be appliedin the reverse direction. paper capacitor Two metal foils as electrodesare clipped on insulated paper and the assembly can be rolled up to forma cylinder that is enclosed inside a metal housing or insulated materialsuch as sealing wax, ceramic or vitreous-enamel. The package is smallerwith higher capacitance. Due to high inherent inductance and loss ofcapacitor, the device is suitable for being applied to low frequencycircuit. metallized The device basically has the same paper capacitorstructure with paper capacitors while a metal membrane is used insteadof metal foil. Its features are small volume and higher capacitance,generally applied to low-frequency circuit. oil impregnated Byimpregnating the paper with special paper capacitor oil, tolerance ofthe capacitor is improved. It features on high capacity and widetolerance. However, the volume of the device is quite large.vitreous-enamel The dielectric material is capacitor vitreous-enamel. Ithas advantages of ceramic capacitors while the volume is smaller. Itwithstands high temperature. ceramic The dielectric is ceramic and thecapacitor plates are made from ceramic base with silver membrane. Itsfeatures are small volume, good thermostability, higher insulationresistance but low capacity. Thus it is used for high frequency circuit.The ferroelectric ceramic capacitor has higher capacity while the lossand temperature coefficient are higher. Thus it is applied to lowfrequency circuit. film capacitor This capacitor has the same structurewith the paper capacitor. The dielectric of the capacitor is polyesteror polystyrene. The polyester capacitor has higher dielectric constant,small volume, high capacity, and good stability thus is suitable forbypass capacitors. While the polystyrene capacitor has small loss, highinsulation resistance but high temperature coefficient. This capacitoris suitable for high frequency circuit. mica capacitor The silverelectrodes or metal foil are plated directly onto the mica dielectric.Several layers of electrodes and mica are laminated and then are castinside the phenolic resin or sealed inside the epoxy. Its properties arelow loss of dielectric, high insulation resistance, low temperaturecoefficient and it is suitable for high frequency circuit. tantalum orTantalum or niobium is used as niobium positive electrode and dilutedsulfuric electrolytic acid works as negative electrode while capacitordielectric is oxide membrane on surface of the tantalum or niobium. Ithas small volume, high capacity, stable performance, long life, highinsulation resistance, and good thermostability. Thus it is applied toequipments with higher requirements of capacitors. semi-variable It'salso called trimmer capacitor. The capacitor device consists of twopieces or two sets of metal spring with dielectric therebetween. Thedistance or area between two metal springs changes while tuning. Thedielectric can be air, ceramic, mica or membrane. variable It isconstructed by a set of immobile capacitor plates called stator, andanother set of plates, connected to a common axis, called rotor and itscapacity changes according to rotation of the rotor. The two-foldcapacitors are two capacitors whose rotors share the common axis. Thedielectric of such capacitor can be air or polystyrene. Capacitors withair dielectric with features of large volume and small loss are used inthe electron tube radios. The variable capacitor with polystyrenedielectric is a compact sealed capacitor, mostly used in the transistorradio.

Solid capacitors with dielectric layer made from ceramic material withhigh dielectric constant have features of environmental protection, lowimpedance, high thermostability, withstanding high ripple current andhigh reliability. Compared with traditional electrolytic capacitors,solid capacitors have higher stability thus explosion may occur lessfrequently.

The most common solid capacitor is multilayer ceramic capacitor (MLCC)manufactured by suspending ceramic powders in liquid and casting into athin green sheet with thickness from 20 um to 5 um or even thinner. Thenmetal electrodes are sieved (screen) printed onto the sheets which arelater stacked with sheets without electrodes alternately to form alaminated structure. After being sintered at high temperature, thedevice becomes a ceramic sinter that provides an extremely high capacityin a small volume. At last, surface of silver terminal electrode isplated with nickel, tin and lead and then the multilayer ceramic issoldered directly onto the printed circuit board.

The present invention provides a solid capacitor that improvesdisadvantages of electrolytic capacitors and increases capacity.

SUMMARY OF THE INVENTION

It is therefore a primary object of the present invention to provide asolid capacitor and the manufacturing method thereof. The capacitorincludes a dielectric layer with a plurality of holes on surface thereofand two electrodes arranged on two sides of the dielectric layerrespectively. The electrodes contact the holes. Due to the plurality ofholes on surface of the dielectric layer, the surface area of thedielectric layer is increased so that the capacity of the solidcapacitor is improved.

It is another object of the present invention to provide a solidcapacitor and the manufacturing method thereof. While manufacturing thecapacitor, a plurality of high temperature volatile matters is mixed onsurface of the dielectric layer and part of the high temperaturevolatile matters is vapored or volatilized during sintering process ofthe dielectric layer so as to form a plurality of holes on surface ofthe dielectric layer. Thus the surface area of the dielectric layer isincreased and the capacity of the solid capacitor is also gettinghigher.

It is a further object of the present invention to provide a solidcapacitor and the manufacturing method thereof that generate amultilayer capacitor by stacking the capacitor repeatedly so as toincrease the capacity.

In order to achieve above objects, a solid capacitor and a manufacturingmethod thereof are disclosed. The solid capacitor is composed by adielectric layer and two electrodes. A plurality of holes formed by anopening process is disposed on surface of the dielectric layer. The twoelectrodes are connected with the dielectric layer through the holes.Due to the enlarged surface area of the dielectric layer, the capacityof the capacitor is increased. The solid capacitor stores charge byphysical means.

BRIEF DESCRIPTION OF THE DRAWINGS

The structure and the technical means adopted by the present inventionto achieve the above and other objects can be best understood byreferring to the following detailed description of the preferredembodiments and the accompanying drawings, wherein

FIG. 1A to FIG. 1D are schematic drawings showing structure of anembodiment in accordance with the present invention;

FIG. 1E is a schematic top view showing an embodiment of the presentinvention with holes coated with conductive object;

FIG. 2 is a schematic drawing showing structure of another embodiment inaccordance with the present invention;

FIG. 3 is a curve chart showing capacity of capacitors with and withoutholes under different frequencies;

FIG. 4A to FIG. 4D are schematic drawings showing structure of amultilayer capacitor in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention provides a solid capacitor for improvingdisadvantages of conventional capacitors such as easily explosions andenvironmental pollutions by means of larger surface area for increasingstored charge. And the solid capacitor is a device that stores thecapacity of a physical system.

Refer from FIG. 1A to FIG. 1D, structure of a solid capacitor 1 inaccordance with the present invention is disclosed. In the beginning, adielectric green tape 10 is sintered into a dense dielectric layer 100.The temperature for sintering ranges from 600 degrees Celsius to 1700degrees Celsius. Then two sides of the dense dielectric layer 100 arecoated with a plurality of dielectric 20 that is mixture of a pluralityof high temperature volatile matter 30 or a plurality of conductiveobjects. The dense dielectric layer 100 and the dielectric 20 aresintered at an operating temperature of 300 to 1700 degrees so as tomake the dielectric 20 form a loose dielectric layer 200. After the hightemperature volatile matter 30 being volatilized, a plurality of holes300 connected with the outside are formed on surface of tow sides of theloose dielectric layer 200. The diameter or width of the hole 300 isbetween 1 nm˜100 μm while the range of 10 nm˜10 μm is preferred. And thebest range is from 5 nm to 50 μm. Therefore, the loose dielectric layer200 with large surface area is formed. Moreover, two sides of the loosedielectric layer 200 are connected with two electrodes 400 respectivelythrough the holes 300. The electrodes 400 are formed on surface of theloose dielectric layer 200 by one of electroplating, electrolessplating, sputtering, spin-coating, coating, printing and chemical vapordeposition (CVD) or by combinations of above techniques.

The density ratio of the loose dielectric layer 200 and the densedielectric layer 100 ranges from 0.05 to 0.95 while the range between0.1 and 0.9 is preferred and the best ratio ranges from 0.15 to 0.85.The material of the dielectric 20 and the dielectric green tape 10 canbe the same or different. The material is selected from ceramicdielectric layer, high molecular dielectric layer, and glass dielectriclayer or various combinations of above material.

The holes 300 are formed on the loose dielectric layer 200, the holes300 are connected to the outside, not the holes inside the loosedielectric layer 200 without contact the outside. Moreover, once thedielectric 20 having the high temperature volatile matter 30, the hightemperature volatile matter 30 can be carbon, organics or theircombinations. After being sintered, the holes 300 of the loosedielectric layer 200 is coated with the conductive object 500, as shownin FIG. 1E. The conductive object 500 can be carbon that works as anelectrical connection between the electrodes 400 and the loosedielectric layer 200. The solid capacitor according to the presentinvention stores charge by physical means.

Furthermore, refer to FIG. 2 & FIG. 1C, the present invention furtherprovides another manufacturing method to produce the solid capacitor. Atfirst, a dielectric green tape 40 including a first dielectric layer 42and two second dielectric layers 44 is formed. The two second dielectriclayers 44 mixed with a plurality of high temperature volatile matter 30or a plurality of conductive objects are disposed on two sides of thefirst dielectric layer 42. The dielectric green tape 40 is sintered soas to make the first dielectric layer 42 become the dense dielectriclayer 100. Also the high temperature volatile matter 30 is volatilizedto form the holes 300 so that the second dielectric layers 44 form theloose dielectric layers 200. The first dielectric layer 42 and thesecond dielectric layers 44 are sintered into dense and loose structurerespectively due to different material they made from. The followingmanufacturing processes are the same with above descriptions.

Moreover, once the second dielectric layers 44 is mixed with the hightemperature volatile matter 30, the high temperature volatile matter 30can be carbon, organics or their combinations. After being sintered, theloose dielectric layer 200 is generated and the holes 300 thereon shouldbe coated with the conductive object 500 for providing an electricalconnection between the electrodes and the loose dielectric layers, asshown in FIG. 1E.

An embodiment is taking as an example for explanation of the presentinvention:

Experiment Group of the Present Invention:

Taking a dielectric green tape and press it under pressure of 100Kg/cm², sintered at 1350 degrees Celsius, the operating time is 2 hours.Thus a dense dielectric layer is formed and two outer sides of the densedielectric layer are coated with dielectric material and carbon fiber(C.F.) at the ratio of 300:1. After being dried at 70 degrees Celsiusfor 10 minutes, the invention is sintered at a temperature of 1350degrees so as to form a loose dielectric layer with the thickness of0.09 mm.

Control Group without the Loose Dielectric Layer:

The green tape is pressed under 100 Kg/cm², at a temperature of 1350degrees Celsius, the operating time is 2 hours.

Capacitance Frequency Experimental Control (Hz) group group  10K 48051874  50K 3480 1766 100K 3137 1760 500K 2781 1736 1000K  2462 1650

Refer to FIG. 3, the curves shows capacity of capacitors with or withoutholes under different frequencies respectively. As shown in figure, thefirst curve S1 and the secondary curve S2 represent capacity ofcapacitors with and without holes respectively under differentfrequencies. Compared the curve S1 with the curve S2, it is obvious thatthe capacitor with holes has higher capacity than the capacitor withoutholes under different frequencies.

In addition, a solid capacitor according to the present invention can bea multilayer capacitor for demanding of higher capacity. As shown fromFIG. 4A to FIG. 4D, firstly, the solid capacitor 1 in accordance withthe present invention is manufactured as structure in FIG. 4A, thelength of two loose dielectric layers 200 of the solid capacitor 1 areshorter than that of the dense dielectric layers 100 and a firstelectrode 210 as well as a second electrode 220 is disposed thereof.This is a basic unit. Then a first solid capacitor 600 is arranged on asecond solid capacitor 700 reversely and the second electrode 220 iselectrically connected with a third electrode 710 of the second solidcapacitor 700, as shown in FIG. 4B. Thus a repeated unit 800 is formed.

Then the repeated units 800 are stacked repeatedly. A first outerelectrode 810 and a second outer electrode 820 are arranged on twooutsides. The first outer electrode 810 is electrically connected withthe first electrode 210 and a fourth electrode 720 of the seconddielectric layer while the second outer electrode 820 is electricallyconnected with the second electrode 220 and the third electrode 710 soas to form a multilayer capacitor.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details, and representative devices shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

1. A solid capacitor comprising: a dielectric layer portion having atleast one dense dielectric layer and at least two loose dielectriclayers on two outer sides of the dense dielectric layer; a plurality ofholes communicating with the outside are formed by an opening process ineach of the loose dielectric layers, the holes remaining therebypartitioned from the dense dielectric layer; and two electrodes arrangedon two outer sides of the dielectric layer portion, the electrodesextending into the holes for engagement therewith.
 2. The solidcapacitor as claimed in claim 1, wherein the opening process for theholes is a sintering process.
 3. The solid capacitor as claimed in claim1, wherein ratio of the density of the loose dielectric layer to that ofthe dense dielectric layer ranges from 0.05 to 0.95.
 4. The solidcapacitor as claimed in claim 1, wherein ratio of the thickness of therespective loose dielectric layer to that of the dielectric layerportion ranges from 0.01 to 0.45.
 5. The solid capacitor as claimed inclaim 1, wherein ratio of the thickness of the dense dielectric layer tothat of the dielectric layer ranges from 0.1 to 0.98.
 6. The solidcapacitor as claimed in claim 5, wherein diameter of the holes is from0.01 nm to 10 μm.
 7. The solid capacitor as claimed in claim 1, whereinthe dielectric layer portion is mixed with a plurality of conductiveobjects.
 8. The solid capacitor as claimed in claim 1, wherein surfaceof the holes is coated with a plurality of conductive objects.
 9. Thesolid capacitor as claimed in claim 8, wherein the conductive object iscarbon.
 10. The solid capacitor as claimed in claim 7, wherein theconductive object is carbon.
 11. The solid capacitor as claimed in claim1, wherein the solid capacitor stores charge in a physical way byassembly of the two electrodes and the dielectric layer portion.